Re: fitting ballscrew ends

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Leslie Watts" <leswatts@a...>
wrote:

> Marcus,
>
> I also find machining ballscrew ends not really a big deal. I do
> use an offhand grinder to remove most of the hardened land material
> though...saves a bit of time and helps prevent interrupted cutting
> with the carbide tool.
>
> I think part of the issue is the tools available. Perhaps many hobbyists
> do not have lathes with large enough bores to accommodate the screw,
> or they do not have enough rigidity. We don't have that problem...but
> we are not hobbyists.
>
> Here's a thought:
>
> What if there was a pre-machined ballscrew end that just screwed on to
> the unmachined ballscrew end? Internal threads would engage the screw
> ball race area rather than the sometimes non concentric lands.
>
> It would have to be pinned (taper pin) but a pre-drilled hole could
> facilitate
> making the hole. Perhaps some rough offhand ground "flats" in that

area on

> the
> screw would allow the use of ordinary drilling and reaming methods.
>
> I could make such a product...but I have not considered how much it

would

> cost.
> The logistics of having to have many different models for different

screws

> is an issue. The threads would not have to be exactly the same profile
> though...
> just something that engaged a particular pitch and minor diameter in an
> angular
> contact fashion.
>
> What do you think?
>
> Les

I think that for the cost of such an end, someone can find a local
shop to do the work.

But, with a collar, one could heat the end to soften it for the pin.

I really see people messing up putting a pin in though.

I recently took a ball screw, put my propane torch (swirl tip) to it
and got it hot. Burried the end in sand and let it sit a couple
hours. Soft for my 9" lathe.

I went thru 1 carbide cutter per 1/2 inch on the hardened stuff taking
the entire ball thread off in one cut. not letting the tip have an
interupted cut let it cut much longer.

But the softened stuff worked great. did an entire end (4 inches)
with one carbide cutter and it was still like new.

Be that as it may, most people have a small angle grinder, and most
people can make a single axis. Taking a long section of heavy angle
or channel or whatever, one could put the screw in Vee blocks and
rotate it, even by hand, and have the grinder cut. probably with
spring pressure, to a stop.

After looking at the differences, My most likely solution will be to
center drill and drill a hole, then reem it, 1/4 or so, maybe 1/2 the
screw diameter, and about as deep as the screw diameter.

then put in a plug. the full screw diameter, but with a small section
turned down. then weld. butt weld actually.

The added section should be long enough to be on the bearings. the
weld joint should not span the bearings. that puts only torsion on
the weld.

My main concern is to get a perfectly flat shoulder on the screw. I
just didn't like the shoulder that one is left with when cutting the
threads.

I will have the existing shoulder welded so I can make a square and
full height shoulder.

If I was to make a sleeve type extension, I would open the section
with at least two cuts so one could weld the end of the extension on
the threads, but also weld the end of the screw where it hits the
blind hole in the extension.

Whatever is done, I just do not see high forces with the screws. I
have found the screw lenght dictates the diameter more than anything,
and the screw strenght is so far stronger than the machines that even
an end with set-screws would work.

Dave